Method of manufacturing, by photographic means, external, electrically conductive noble-metal patterns on non-metallic, electrically non-conductive, macromolecular supports and products obtained by these methods



h nited States itlatn i 3,223,525 ldti'lilfli) F MANUFACEURWG, BY PHUTO-Rr-tPl-lilt? MEANS), EXTERNAL, ELEQTRICALLY CUNDUCTEVE NQBLE-METALFAETERNS 0N NON-METALLIQ, ELEQTRKCALLY NGNN= DUCZEVE, MACRQIvdULECULARSUPPGRTS AND PRODUQTS OETAINED BY THESE METHEDS Hendrik ionizer andCorneiis .lehannes Dippel, Eludhoven, Netherlands, assignors to NorthAmerican Philips Company, llnc., New York, NFL, a corporation ofDelaware No Drawing. Filed duly 11, 1969, Ser. No. 41,79 Claimspriority, application Netherlands, Study 22, 195?, 241,541 29 Claims.(Cl. 96-35) The invention relates to a method of manufacturing, =byphotographic means, external, electrically conductive noble-metal layerson at least superficially non-metallic, electrically non-conductive,slightly hydrophilic or at least superficially hydrophilizedmacro-molecular supports and to products obtained by this method.

In the method of the invention there is used a lightsensitive layer,which contains at least one light-sensitive compound which is convertedby the reaction of light into a light-reaction product and which, assuch, can be physically developed or which is capable of forming, in asecondary reaction, physically developable metal germs, the metalforming the erm image being provided, as a compound, in the layer eitherprior to the exposure or being added to the layer subsequent toexposure, the metal germ image formed being intensified by means ofstabilized, purely physical development.

The term noble-metal layers is to be understood to mean herein not onlylayers having an uninterrupted surface of a noble metal but also thelayers having patterns having continuous or discontinuous portions, forexample, station-name dials for radio apparatus, ornamental objects,printed wirings, printed circuits and so forth.

The term purely physical development referred to above is to beunderstood to mean the intensification of a weak, photographic metalgerm image into an image of the desired optical density or with therequired quantity of image metal by treating said weak germ image with adeveloping solution containing photographic reducing agents, andreducible compounds of metals nobler than copper, for example, silver,gold, platinum and so forth. A frequently used physical developer is,for example, a solution of silver nitrate in water, to which is addedmetol, hydroquinone or p-phenylene diamine. To such a developer arefurthermore added, as a rule, other substances, in order to improve thepreservability or to control the speed of development, for example,organic acids, butler mixtures or substances reacting with thenoblemetal compound while forming complex ions. During the physicaldevelopment free noble metal, formed by reduction from noble-metal salt,is deposited on the photographic metal germ image, which may lead to aconsiderable intensification of this image.

Purely physical developers, however, in contradistinction to chemicaldevelopers, are unstable systems, since between the noble-metal compoundand the reducing agent there may occur, apart from the heterogenousreaction at the photographic metal germ image in the solution a furtherhomogeneous reaction which gives rise to the spontaneous formation ofnoble-metal germs. Thus, these developers, even if not used, rapidlydeteriorate while separating out noble metal. During the developingprocess a noble-metal deposit, a so-called superficial fog may be formedfrom the developer even on the nonexposed parts of the exposed layer. Inthe literature it is 323,525 Patented Dec. 1 3-, 1955 thereforerecommended to clean the surface of the developed layer with the aid ofa plug of cottonwool (J. M. Eder: Rezepte, Tabelle andArbeitsvorschriften 1415 Aufiage. (1933), page 86, and Eder:Ausfuhrliches Handbuch der P'hotographie Ill, 2, 6, Anti. (1930), page229).

However, it is possible to manufacture comparatively stable physicaldevelopers in accordance with the criteria applied to physicaldevelopment, the spontaneous decomposition thereof being considerablydelayed, so that they may be used for a materially longer time. For thispurpose use may be made of the addition of one or more suitable,so-called ionic, surface-active compounds to the physical developer intowhich there may be added a non-ionic, surface active compound.

A physical development in which use is made of th stabilizing effect ofionic, surface-active substances in conjunction or not in conjunctionwith a non-ionic, surface-active compound is termed herein a stabilizedphysical development. If the use of these surface-active compounds inthe physical development is dispensed with, reference is made herein tonon-stabilized physical development. Such stabilized physicaldevelopment is shown in copending U.S. application Serial No. 845,098.

In a copending application a method has been described, which uses alight-sensitive layer which does not contain, during the exposure, ametal compound forming a germ image and in which, by the exposure, alight-reaction product is formed which is capable, in a secondaryreaction, of setting free metal from a solution of a mercurous or silvercompound. In this method is used a special, so-called mirror exposure,after which the layer is contacted with a solution of the said metalcompound (the so-called germ introduction bath), so that an at leastpartly external metal germ image (lying on the surface of the support)is formed, this external metal germ image, upon intensification by meansof non-stabilized, purely physical development, grows into an external,electrically conductive noble-metal layer. The external metal germ imagedoes not grow into an external, electrically conductive noble-metallayer, however, if it is subjected to a treatment with a stabilized,purely physical developer.

The term mirror exposure is to be understood to mean that exposureenergy per surface unit of the light-sensitive layer which, at thechosen concentration of metal ions in the germ introduction bath,provides an at least partly external metal germ image, which afterintensification by means of a chosen non-stabilized, purely physicaldeveloper, provides, under chosen conditions of temperature anddeveloping time, an external noble-metal layer which exhibits anelectric resistance not exceeding 18 ohms per square.

in accordance with the invention electrically conductive, noble-metallayers may be manufactured, by photographic means, on at leastsuperficially non-metallic, electrically non-conductive, at leasthydrophilized macromolecular supports, which noble-metal layers have anexcellent adhesion to the support and a beautiful gloss.

According to the invention applicants have unexpectedly found that whenone of said non-conductive supports is treated with a light sensitivecompound such as a silver halide or one which produces, upon exposure tolight, a light reaction product capable of producing in the presence ofwater silver or mercury germs from water soluble silver and mercurycompounds either present before or after exposure and this layer isexposed to light for a certain critical minimum exposure energy calledherein the outgrowth exposure and the layer after the silver or mercurygenn image is formed is developed with a stabilized physical developerfor a prolonged period of time the internal image which has been formedbefore physical development is made to grow out beyond the surface ofthe support and become an external image having a resistance of lessthan 10 ohms per square.

In contradistinction to the method, in which use is made of a mirrorexposure, and an at least partly external metal germ image is obtainedand this image is caused to grow by nonstabilized, physical developmentinto an external noble-metal layer, a substantially only internal metalgerm image is, in accordance with the invention, intensified bystabilized physical development, or else only the internal portion of apartly external metal germ image, is intensified by stabilized physicaldevelopment, While initially an internal, neutrally grey to blacknoble-metal image is formed, which, upon a prolonged stabilizeddevelopment, grows into an external, electrically conductive noble-metallayer, which exhibits an improved adhesion to the support and, as arule, a more beautiful gloss than such a layer obtained by the methoddescribed in the copending application. In accordance with the method ofthe invention appreciably longer developing times are, as a rule,required than in the known method.

By electron-microscopic investigation it was determined that under theseconditions, in a stabilized physical developer only the internal metalgerm image formed grows and that this growth, if the development is notprematurely interrupted, continues until the noble-metal image projectsfrom the support, after which it constitutes an external, electricallyconductive noble-metal layer according to the image pattern. Such aprolongation of the physical development not disturbed by spontaneousnoble-metal deposition has become possible, in a simple manner, only byusing stabilized development.

It was a great surprise to find that while an external metal germ imagesubstantially does not grow in a stabilized physical developer, aninternal metal germ image grows in such a developer and upon projectingfrom the support does not stop growing but grows on undisturbedly forsome time.

Consequently, the method according to the invention has the greatadvantage that now for the manufacture, by photographic means, ofexternal, electrically conductive noble-metal layers use may be made ofstabilized, purely physical development.

Since the development of an internal metal germ image into an external,electrically conductive noble-metal layer requires, as a rule, anappreciably longer time than the development of such a germ image intoan internal, photographic image for more conventional uses or thenonstabilized development of an at least partly external metal germimage into an external noble-metal layer, the activity of the developeris required to be accelerated in order to reduce the developing time.This may be achieved by using a higher developing temperature, bychoosing higher concentrations of the noble-metal compound and/or of thephotographic reducing agent in the developer, of a higher pH of thedeveloper, and so on than is common practice for the development ofnormal internal images. With stabilized physical development this may,as a rule, be achieved without troublesome spontaneous formation ofnoble-metal germs. Owing to this activation of the developer thedevelopment into an external image can be accelerated by a factor 10 to20.

The exposure energies to be employed to obtain photographic metal germimages which grow, upon a prolonged stabilized purely physicaldevelopment, into external, electrically conductive noble-metal layerswith reproducible properties, are termed herein outgrowth exposures. Theterm outgrowth exposure is to be understood to mean herein that exposureenergy per surface unit of the light-sensitive layer which, with achosen photographic system and with a chosen composition of thelight-sensitive layer, yields a photographic metal germ image, which,upon intensification in a stabilized, physical developer obtained bydissolving, in distilled water,

4.- Metol mol/litre 0.025 Citric acid do 0.100 Silver nitrate do 0.010Lissapol N percent by weight 0.02 Armac 12D do 0.02

at a developing temperature of 20 C. within 180 min., the developerbeing refreshed each time after one hour, grows into an external,electrically conductive noble-metal layer which, after washing in waterhas a resistance not exceeding 10 ohms per square.

When with a chosen photographic system the outgrowth exposure has oncebeen determined, any other stabilized physical developer is capable ofproviding an external, electrically conductive noble-metal layer bydeveloping for such a long time that the resistance of the noble-metallayer is at the most 10 ohms per square.

The physical development may be carried out, as stated above, as analternative with aid of a stabilized, physical developer which has beenactivated to shorten the developing time.

Many uses of the external noble-metal layers produced in accordance withthe invention on non-metallic, electrically non-conductive,macro-molecular supports are found in the electrical andelectro-technical fields. In these cases it is frequently important thatthe electric resistance should not exceed by far that of correspondinglayers containing the same quantity of noble metal in compact state andthat this resistance should not vary much in the course of time. Thenoble-metal layers obtained after physical development usually do notfulfill this requirement without the need for further means. By athermal and/or chemical after-treatment and/or a mechanical polishingtreatment the high resistance value can be reduced to a materiallylower, reasonably constant and reproducible value.

The thermal after-treatment is carried out by heating the noble-metallayer at a temperature of at least C. The desired effect is attainedmore rapidly with an increase in temperature but the effect of thetemperature on the material of the support must be considered. Thechemical after-treatment to reduce the electric resistance of externalsilver layers consists in bringing these into contact with an aqueoussolution containing one or more compounds separating off a hydrogen ionor a potential determining anion with respect to the silver metal, forexample (31 BF, J'-3, CNS CN 3, 8 803 S203: 01 OH. Mechanical polishingof the layer reduces, in many cases, the electric resistance of thelayer to a sufficient extent. Moreover, such a treatment improves theoptical decorative properties of the noble-metal layer.

A great number of uses both in the electrical and in the decorationfield require or desire that an external noble-metal layer obtained bythe method according to the invention should be subjected to anelectro-chemical aftei treatment, after which a superficial chemicalconversion or coloration may be carried out. For this purpose use may bemade, for example, of electrolytic polishing, electrolytic deposition ofmetals, while use is made or not made of an external current source,electrolytic coloration of the deposited metal or electrophoreticcoating with a protective or insulating or photoand/ or semiconductivesurface layer. If desired, a combination of various electro-chemicaland/ or chemical after-treatments is possible. For various uses a choicemay furthermore be made from a great number of mechanical after-treatments, which may be combined with the after-treatments described above.A few important suitable after-treatments of this kind are, inter alia:polishing of the surface, application of a lacquer or varnish layer tothe layer surface, embedding of the layer, together with the support, inan insulating envelope of thermo-hardening or thermoplastic material,transfer of the layer, if necessary together with the support, to adifferent, support of high electrical qualities, also ofthermo-hardening or thermo-plastic material, application of electricalconnections by soldering (for example, dip soldering).

In the electronics field use may be made, for example, of externalnoble-metal layers manufactured according to the invention, inconjunction with one or more of the aforesaid after-treatments, for themanufacture of printed wirings, circuits, screen grids, switches andother component parts.

The method according to the invention may, consequently, be carried outby means of all those photographic materials in which, by exposure, aphysically developable metal germ image can be obtained directly orindirectly. These materials are, in the first place, those which containa light-sensitive compound of which the light-reaction product behaves,as such, i.e. without previous chemical conversion, as a physicallydevelopable photographic metal germ image, for example, the materialscontaining, as a light-sensitive compound, silver halide. They includefurthermore all photographic materials containing a light-sensitivecompound of which the light-reaction product, as such, cannot bephysically developed, this product being, however conversible, in asecondary reaction, into a physically developable, photographic metalgerm image, while the metal forming the germ image is contained in thephotographic layer in the form of a compound prior to exposure. Thissecondary reaction, if the light reaction product is a metal compound,will consist in setting free metal germs therefrom, as is, for example,the case with the photographic process in which use is made of thelight-sensitivity of the so-called Eder solution and in which thelight-reaction product consists of mercurous chloride. An importantgroup of photographic materials which may be employed in the methodaccording to the invention are the materials containing alight-sensitive compound of which the light-reaction product, in asecondary reaction, is capable of setting free physically developablemercury or silver germs from mercurous or silver compounds respectively.

This secondary reaction may be based on a so-called disproportioning ofmercurous ions in accordance with the reaction equation:

Free mercury is formed since the light reaction product reacts withmercuric ions. Or it may be based on the reduction of silver ions inaccordance with the equation:

The mercury atoms or silver atoms set free respectively unite to formmercury or silver germs respectively.

In these systems the mercurous compound or the silver compound may beprovided prior to exposure in the layer containing the light-sensitivecompounds (US. Patents 2,067,690 and 2,738,272) or a solution of such acompound may be brought into contact with the layer after the latter hasbeen exposed. The last-mentioned variant is termed germ introductionmethod and the solution of the metal compound by which the introductionof the germs is carried out is termed germ introduction bat (US. Patent2,764,484).

In the germ introduction method the light-sensitive compounds of theclass of the aromatic diazosulphonates are particularly useful, moreparticularly in conjunction with so-called anti-regression agents, i.e.substances which, when added to the layer, prevent diazosulphonate frombeing reformed from its light-reaction product by binding either thesulphite or the diazoniurn radical or both so that the sulphite remainscapable of reacting with the mercurous compound while forming mercurygerms With this method the gloss and the reproducibility of theexternal, electrically conductive noble-metal layers may be furtherimproved by adding to the germ introduction bath, apart from themercurous compound, one or more organic hydroxy acids selected from thegroup citric acid, tartaric acid, glycolic acid, glycerol acid and malicacid. Then, at least such a quantity of the acid is to be added that theprecipitate initially forming with the mercurous compound redissolves.

Other suitable, light-sensitive compounds, of which the light-reactionproduct sets free, in a secondary reaction, physically developablemercury germs from a mercurous compound, are, for example,o-hydroxy-benzene-diazo nium compounds, o-hydroxy-naphthalene diazoniumcompounds, aromatic diazocyanides, oand p-nitro-mandelic acid-nitril,the bisulphite compounds of oand p-nitrobenzaldehyde, a series ofinorganic, complex compounds from which, by exposure, one or more of thefollowing ions or molecules are set free:

pyridine and derivatives thereof, thiourea and derivatives thereof,which ions and molecules are bound to at least one central metal ion.The light-reaction product of ohydroxy-benzene-diazonium compounds andof o-hydroxynaphthalene diazonium compounds is also capable of settingfree physically developable silver germs from silver compounds.

Also suitable are furthermore certain azines, thiazines and oxazinecompounds, salts of monoand disulphonic acids, of naphthoquinone and ofanthraquinone and certain diazonium compounds, such as amino-l-diethoxy-2,5-benzene-diazonium borofluoride-4, of which the lightreactionproduct, in a secondary reaction, is capable of setting free silvergerms from silver compounds.

Suitable materials which may be used for the supports in carrying outthe method according to the present invention are, in general, allfilm-forming high polymer products, which if not yet so, are renderedsuperficially accessible to a certain extent for the various baths, forexample, gelatin, regenerated cellulose paper, wholly or partlysaponified cellulose esters, polyvinyl alcohol, and so forth.

The invention will now be described in greater detail with reference tothe examples which follow.

Example I A superficially saponified cellulose triacetate foil wassensitized by impregnating it for two minutes in an aqueous solutioncontaining 0.15 mol of o-rnethoxy-benzenediazosulphonic acid sodium and0.1 mol of cadmium lactate per litre, after which it was wiped off anddried. Strips of this foil were then exposed behind a line negative withthe aid of a high-pressure mercury-vapour lamp and a sensitometer, afterwhich they were treated for a few seconds with an aqueous solutioncontaining 0.005 mol of mercurous nitrate and 0.01 mol of nitric acid.Then the strips were washed for a short time in distilled water anddeveloped in a stabilized, physical developer, obtained by dissolving indistilled water:

Metol (0.025 mol/litre) Citric acid (0.1 mol/litre) Silver nitrate (0.01mol/litre) Lissapol N (0.02% by weight), and Armac 12 D (0.02% byweight) Lissapol N is a condensation product of alkylphenols andethylene oxide, containing a polyethylene chain; Armac 12 D is a mixtureof dodecyl and tetradecylamine acetate. By using a developingtemperature. of 20 C., a developing time of 180 min., the developingbath being refreshed after 60 and min., respectively, the minimumoutgrowth exposure was determined, i.e., the minimum exposure energy perunit of the light-sensitive layer, having, after this development, anoutgrown silver layer with an electric resistance which sufiices theaforesaid criterion.

With a developing time of 15 min. in a developer of the aforesaidcomposition the tested exposure region (1 to 2 times the minimumoutgrowth exposure) yielded only internal silver images. The densitiesof the images obtained with the maximum exposures were, in this case,however immeasurably high.

With a developing time of 30 min. in the said developer, however, anexposure 2V2 times higher the minimum outgrowth exposure produced anoutgrown, electrically conductive silver layer was obtained. Exposuresof 2 /22 times the minimum outgrowth exposure produces sliver layerswith electric resistances from 1900 to 340 ohms per square, whichvalues, after a thermal treatment of one hour at 150 C., dropped to 1.2and 0.2 ohms per square surface respectively.

With a developing time of 60 min. an exposure being only /2 times theminimum outgrowth exposure produced an outgrown electrically conductivesilver layer. The resistance values measured decreased, with anincreasing exposure to 2 times the minimum outgrowth exposure, from 400to 120 ohms per square. After the thermal treatment these values haddropped to a few tenths ohms per square.

Oubgrown silver layers having electric resistances as stated above couldbe intensified with copper by electrolytic means, while use was made ofan aqueous copperdeposition bath of the following composition:

Copper sulphate 5 aq. (200 g./litre) Concentrated sulphuric acid (50g./litre), and Phenolsulphonic acid sodium (0.5 g./litre) Use was made,for example, of a copper-deposition time of 2 min. with a currentdensity of 5 A./dm. Copper layers thus obtained could then beelectrophoretically coated superficially, for example, with a layer ofalumina, by using a suspension of of Alundum in methanol with a fieldintensity of 37.5 v./cm. for 6 sec. and 3. current of 70 ma.Electrolytic intensification with nickel could take place, for example,by means of an aqueous nickel-coating bath containing, per litre, 240 g.of nickel sulphate, 45 g. of nickel chloride and 30 g. of boric acid.The operational temperature of this bath was 40 C. and the currentdensity amounted to 2 to 4 A./dm.

Many other compositions of stabilized, physical developers, yieldedcorresponding results. Two very suitable compositions are mentionedhere, in particular:

(a) 2 g. of hydroquinone, 0.1 g. of citric acid, 0.2 g. of silvernitrate and 0.2 g. of Aresklene 400 (dibutyl- 'orthophenyl-phenol-sodiumdisulphonate) per 100 g. of

distilled water,

(b) 0.5 g. of metol, 2 g. of citric acid, 0.2 g. of silver nitrate, 0.02g. of Sapamine KW and 0.03 g. of Alamac 26 D in 100 g. of distilledwater. Sapamine K is the methyl sulphate ofmonostearylamido-ethylene-trimethylamine; Alamac 26 D is a mixture ofoleyl stearyl and palmetyl-amine-acetate.

The activity of the said developers can be kept substantially constantfor a satisfactory time by refreshing the silver nitrate used for theimage formation from time to time in the form of small quantities of a10% by weight of an aqueous solution of silver nitrate. By reducing thequantity of citric acid in the developer (b) to 0.067 g. and byincreasing the quantity of silver nitrate to 0.4 g., a developer wasobtained which yielded, within a few minutes an outgrown,electrically-conductive silver layer.

Sensitizing solutions containing other light-sensitive diazo-sulphates,for example, p-methoxy-benzene-diazosulphonic acid sodium ordimethoxy-Z.S-benzene-diazosulphonic acid sodium-1 and/ or otheranti-regression means, such as resorcinol, yielded correspondingresults.

Example 11 Unilaterally white, woodfree litho-paper was sensitized byimpregnation, on one side, in the solution of a light-sensitive compoundas described in Example I and by drying it. The exposure, the treatmentwith the mercurous nitrate solution and the stabilized physicaldevelopment at a temperature of 20 C. of strips of this material tookplace in the manner described in the preceding example. In order todetermine the minimum mirror exposure, moreover, a few strips weredeveloped for 10 minutes at 20 C. in a non-stabilized physical developerobtained by dissolving, in distilled water, metol, citric acid andsilver nitrate with concentrations as indicated in the first developerof Example I. With a developing time of 20 min. in a stabilized physicaldeveloper and with an exposure of 8 times the minimum mirror exposure nooutgrown, electrically conductive silver layer was obtained. \Vith adeveloping time of 30 min. in the said stabilized developer, however, anexposure of even 8 times lower the minimum mirror exposure yielded anoutgrown, silver layer with an electrical resistance of 2100 ohms persquare. When using an exposure equal to the minimum mirror exposure, theelectric resistance of the silver layer obtained amounted to only 180ohms per square, which value, after a treatment at 150 C. for one hour,dropped to about 1.5 ohms per square.

Such a silver layer, which had been manufactured in the pattern of ascreen grid, was intensified for 15 min. with a current density of 4A./dm. electrolytically with copper by means of an acidiccopper-deposition bath containing 20% by weight of copper sulphate (SHO) and 6% by weight of sulphuric acid in distilled water. After washingand drying and soldering to a mounting strip, the copper-coated grid wasdipped in a polyvinyl-chlorideacetate lacquer and again dried. Then apolyvinylchloride foil of about 25 was applied to the image side and theassembly was compressed for one minute at C. under a pressure of 10kgs./cm. The insulated, flexible grid thus obtained could be readilybent into the form of a cylinder and be thus used as a screen grid forelectric coils.

Example Ill The support material of Example I was sensitized byimpregnating it for two minutes in an aqueous solution containing 2% byweight of anthraquinone-disulphonic acid sodium-2,7, after which it waswiped off and dried. Strips of this light-sensitive material wereexposed with the aid of a high-pressure mercury-vapour lamp behind aline negative and then treated, for 15 sec., with an aqueous solutioncontaining 0.01 mol of silver nitrate and 0.2 mol of acetic acid acetatebuffer.

The pH of this solution was 6. Then the strips were washed, for threeminutes, in distilled water and. developed in a stabilized physicaldeveloper as described in Example I. For developing time longer than 60or 120 minutes respectively, the developing bath was refreshed after 60min. or after 60 and 120 min. respectively.

When an exposure of 16 times that of an exposure energy E, which hadyielded an internal density of about 2 after a developing time of 15min. was used, even in a developing time of 15 min., no external,electrically conductive silver layer was formed, but a very highinternal density. After 60 min. of development the strip exposed to 16Eexhibited an outgrown silver layer having an electric resistance ofabout 400 ohms per square, which value, after a thermal treatment (at C.for one hour) dropped to about 2 ohms per square. After 105 min. ofdevelopment the outgrown silver layer had an electric resistance ofabout 350 ohms per square which value dropped, after rubbing with a plugof cottonwool, to about 100 ohms per square. After min. of developmentthe resistance of the silver layer obtained amounted to about 300 ohmsper square. The last-mentioned value dropped, after a treatment, for oneminute, with a 0.1 N solution of potassium chloride in water to about2.7 ohms per square.

The use of the exposure of the time E yielded, after 60 min. ofdevelopment, a silver layer with a resistance of about 2250 ohms persquare. After the said thermal treatment this value dropped to 5.3 ohmsper square. After 165 min. of development a silver layer with aresistance of about 750 ohms per square was obtained. After theaforesaid chemical treatment, this value was 13 ohms per square.

Similar resistance-reducing effects could be achieved by replacing thetreatment with the potassium chloride solution by one of the solutionsof the following compounds: sodium bromide, Sodium iodide, sodiumthiosuphate, sodium sulphite, sulphuric acid, potassium hydroxide,potassium thiocyanide and sodium sulphide.

Example IV The support material of Example I was sensitized byimpregnating it for two minutes in an aqueous solution containing 0.4mol of hydroxy-l-diazo-Z-methyl-G-benzene-sulphonic acid-4, 0.05 mol ofmercurous nitrate and 0.1 mol of nitric acid per litre, after which itwas wiped off and dried. Strips of this material were exposed with theaid of a high-pressure mercury-vapour lamp and then treated, for a fewseconds, with distilled water. Then the strips were developed in thestabilized physical developer of the composition referred to in thepreamble of Example I. Eventually the developing bath was refreshedafter 60 and 120 min. respectively. Finally the developed strips werewashed for about 10 min. in distilled water and dried in air.

When using an exposure of about twice the minimum outgrowth exposure,after a developing time of 30 min., an outgrown, electrically conductivesilver layer was obtained. The electric resistance of the externalsilver layer obtained could be reduced by thermal or chemicalaftertreatment or a mechanical polishing treatment to a considerableextent. When using an exposure of about 4 times the minimum outgrowthexposure, after a developing time of 7.5 min., an internal density ofabout 2 was obtained. When using an exposure of about 64 times theminimum outgrowth exposure, after a developing time of 7.5 min., a veryhigh internal density was obtained.

Example V The support material of Example I was sensitized byimpregnation for 2 min. in an aqueous solution containing 3% by weightof hydroxy-l-diazo-2-naphthalenesulphonic acid-4, 2% by weight of citricacid and 4% by weight of silver nitrate, after which it was wiped offand dried. Strips of this material were exposed behind a line negativewith the aid of a water-cooled high-pressure mercury-vapour lamp andthen washed for two minutes in distilled water. Then the strips weredeveloped in a stabilized physical developer of the comparison indicatedin the first recipe of Example I. The developing bath was refreshedafter 60 and 120 min. respectively. Finally the strips were washed againand dried in air. With an exposure yielding, after a developing time of7.5 min. an internal density of about 2, an outgrown silver layer wasobtained after 30 min. of development, the electric resistance thereofbeing 980 ohms per square, which value dropped, after a thermaltreatment at 150 C. for one hour, to 0.5 ohm per square and, after achemical treatment in an aqueous solution containing 0.1% by weight ofpotassium chloride, to 1.1 ohms per square. After a developing time of60 min., by using the same exposure, a silver layer was obtained, ofwhich the electric resistance amounted to 340 ohms per square. After thethermal treatment, this value dropped to 0.25 ohm per square. Theminimum outgrowth exposure (developing time 180 min.) was about 32 timeslower than the exposure used above.

Example VI A superficially saponified cellulose tri-acetate foil wassensitized by impregnating it for two minutes in an aqueous solution of5% by weight of mercuric chloride, 5% by weight of ferric ammoniumoxalate and 2.5% by weight of ammonium oxalate, after which it is wipedoff and dried. Strips of this foil were exposed to the light of ahigh-pressure mercury-vapor lamp and then treated for 10 sec. with a 10%by weight solution of sodium sulphite in water and for 1 min. withdistilled water. Then the strips were developed in the stabilizedphysical developer of Example I. The developing bath was refreshed after60 and min. respectively. Finally the strips were washed for 10 min. indistilled water and dried in air.

When using an exposure of 32 times E (that exposure which yielded, aftera developing time of 7.5 min. an internal density of about 2), also witha developing time of 7.5 min., no external, electrically conductivesilver layer was obtained, but a very high internal density.

After 30 min. of development, an outgrown, electrically conductivesilver layer was obtained on the strips subjected to exposure E. Theminimum outgrowth exposure was 3 to 4 times lower than the exposure E.

The electric resistance of the external silver layers obtained could bereduced also in this case to a considerable extent by a thermal or achemical after-treatment or mechanical polishing.

Example VII Strips of an optically not-sensitized silver halide film ofthe firm of Gevaert, known under the trademark of Scientia 14 B 50, wereexposed preferably with the aid of a mercury-vapour lamp, behind a linenegative.

After the exposure the strips were fixed for 5 min. in an aqueoussolution containing 5% by weight of anhydrous sodium sulphite andcarefully washed in distilled water. Then the strips were developed inthe stabilized physical developer used in the preceding example. Whenthe developing time was longer than 60 and 120 min. respectively, thedeveloping bath was refreshed after 60 and 120 min. Finally the stripswere again washed and dried in air. After 45 min. of development anoutgrown, electrically conductive silver layer was obtained, when usingan exposure of 225 times the minimum outgrowth exposure (developing timemin.) the exposure intensity being approximately half that of theexposure yielding, after 15 min. of development, a density of about 2.After 60 min. of development an outgrown, electrically conductive silverlayer was formed when using an exposure of 28 times the minimumoutgrowth exposure. After 75 min. of development, already with anexposure of 23 times the minimum outgrowth exposure, an electricallyconductive layer was obtained.

With a similar film of the firm of Ilford, i.e., 5 B 11, similar resultscould be obtained, be it in this case that the latent image grew outslightly more rapidly, so that shorter developing times could sufiice.

With the diapositive contrast plate of the firm of Gevaert only after adeveloping time of 100 min. in the aforesaid, stabilized physicaldeveloper, an outgrown, electrically conductive silver layer could beobtained, when the exposure was carried out with the aid of amercury-vapour lamp. The anti-halo layer was removed, in this case priorto fixation, by treating it with an ammonia solution.

Also on a photographic enlarging paper of the firm of Agfa trademarkBrovira, a similar method, using a developing time of at least 30 min.could provide an outgrown, electrically conductive silver layer. Thedeveloper had, in the latter case, the following composition: 1.6% byweight of metol, 3.2% by weight of citric acid, 0.4% by weight of silvernitrate, 0.02% by weight of Lissapol N and 0.02% by weight of Armac 12 Din distilled Water.

The electric resistances of all these silver layers could be reduced, bythermal or chemical after-treatment or by mechanical polishing, to aconsiderable extent.

While we have described our invention in connection with specificembodiments and applications, other modifications thereof will beapparent to those skilled in this art without departing from the spiritand scope of the invention as defined in the appended claims.

What is claimed is:

1. A method of producing by photographic means an external electricallyconductive noble-metal pattern on an at least superficiallynon-metallic, electrically nonconductive, at least slightly hydrophilicmacro-molecular support comprising the steps of sensitizing said supportWith at least one light-sensitive compound selected from the groupconsisting of the silver halides and those organic compounds the lightreaction products of which are capable of reacting in the presence ofwater with a water soluble metallic compound selected from the groupconsisting of water soluble silver and mercurous compounds to form freesilver and mercury metal at the exposed portions, said water solublemetallic compound being present prior to development, selectivelyexposing said support for a time at least equivalent to an outgrowthexposure, treating said selectively exposed support with said watersoluble metallic compound in the presence of moisture, thereby formingan internal latent image containing free metal selected from the groupconsisting of silver and mercury at the exposed areas and physicallydeveloping said latent image by treatment with a developing solutioncomprising an aqueous solution of a water soluble reducible salt of anoble metal selected from the group consisting of silver, gold andplatinum, said developing stabilized solution being stabilized with anionic surface active compound for a time at least sufiicient to causesaid internal image to grow into an external electrically conductivepattern of said noble-metal.

2. The method of claim 1, wherein the external electrically conductivepattern of the noble-metal is heated at a temperature of at least 80 C.

3. The method of claim 1, wherein the resultant noblemetal pattern is asilver layer and is treated with an aqueous solution of at least onecompound having a potential determining anion with respect to the silvermetal.

4. The method of claim 1, wherein the resultant noblemetal pattern istreated with an aqueous solution of a member selected from the groupconsisting of non-oxidizing acids and acid salts.

5. The method of claim 1, wherein the resultant noblemetal pattern issubjected to mechanical polishing.

6. The method of claim 1, wherein the noble-metal pattern iselectrolytically intensified.

7. The method of claim 1, wherein electrophoretically a colloidalmaterial is applied to the metal layer.

8. The method of claim 6, wherein the resultant metal layer is subjectedto polishing.

9. The method of claim 1, wherein the light-sensitive compound is alight-sensitive silver halide.

10. The method of claim 1, wherein the light-sensitive compound is anorganic compound.

11. The method of claim 10, wherein the water-soluble compound isprovided prior to exposure in the layer.

12. The method of claim 10, wherein the water-soluble compound is addedto the layer after the exposure.

13. The method of claim 10, wherein the light-sensitive organic compoundproduces a light-reaction product capable of setting free metallicmercury from a watersoluble mercurous compound, in the presence ofwater.

14. The method of claim 13, wherein the light-sensitive compound is ano-hydroxy-benzene diazonium compound.

15. The method of claim 13, wherein the light-sensitive compound is anaromatic diazo-sulphonate and the lightsensitive layer contains amaterial which prevents the diazo-sulphonate from being reformed fromthe light-reaction products so that the sulphite remains capable ofreacting with the mercurous compound to form a mercury nucleus.

16. The method of claim 13, wherein the aqueous solution of themercurous compound the germ-introduction both there is added an acidselected from the group consisting of citric acid, tartaric acid,glycolic acid, glycerol acid and malic acid, in such a concentrationthat the precipitate formed initially with the mercurous compound isdissolved.

17. The method of claim 10, wherein the light-sensitive organic compoundproduces a light-reaction product capable of setting free metallicsilver from a water-soluble silver compound in the presence of water.

18. The method of claim 1, wherein the light-sensitive compound isapplied to a paper layer.

19. The method of claim 1, wherein the light-sensitive compound isprovided in a cellulose ester layer which is rendered superficiallyhydrophilic by saponification.

20. The method of claim 13, wherein the light-sensitive organic compoundis an o-hydroxy-naphthalene diazonium compound.

References Cited by the Examiner UNITED STATES PATENTS 2,067,690 1/1937Alink et al. 9649 2,317,591 4/1943 Cramwinckel et al. 9663 2,738,2723/1956 Jonker et al. 9649 2,750,292 6/1956 Dippel et al. 9688 X2,854,386 9/1958 Lyman.

FOREIGN PATENTS 157,182 6/1954 Australia. 167,781 6/ 1954 Australia.

OTHER REFERENCES Alink et al.: Journal of the SMPTE, volume 54, March1950, pages 345-366.

Eastman Kodak Abstracts 0177, abstract of P. Lazenby, Outline ofPhysical Development, Miniature Camera World, vol. 1, pages 457458, 460and 462, August 1937.

Eastman Kodak Abstracts 0177-65, abstract of R. Namias, PhysicalDevelopment, 11 Progreso Foto grafico, vol. 41, pages -169, June 1934.

NORMAN G. TORCHIN, Primary Examiner.

MILTON STERMAN, PHILIP E. MANGAN,

Examiners.

1. A METHOD OF PRODUCING BY PHOTOGRAPHIC MEANS AN EXTERNAL ELECTRICALLYCONDUCTIVE NOBEL-METAL PATTERN ON AN AT LEAST SUPERFICIALLYNON-METALLIC,ELECTRICALLY, NONCONDUCTIVE, AT LEAST SLIGHTLY HYDROPHILICMACRO-MOLECULAR SUPPORT COMPRISING THE STEPS OF SENSITIZING SAID SUPPORTWITH AT LEAST ONE LIGHT-SENSITIVE COMPOUND SELECTED FROM THE GROUPCONSISTING OF THE SILVER HALIDES AND THOSE OGANIC COMPOUNDS THE LIGHTREACTION PRODUCTS OF WHICH ARE CAPABLE OF REACTING IN THE PRESENCE OFWATER WITH A WATER SOLUBLE METALLIC COMPOUND SELECTED FROM THE GROUPCONSISTING OF WATER SOLUBLE SILVER AND MERCUROUS COMPOUNDS TO FORM FREESILVER AND MERCURY METAL AT THE EXPOSED PROTIONS, SAID WATER SOLUBLEMETALLIC COMPOUND BEING PRESENT PRIOR TO DEVELOPMENT, SELECTIVELYEXPOSING SAID SUPPORT FOR A TIME AT LEAST EQUIVALENT TO AN OUTGROWTHEXPOSURE, TREATING SAID SELECTIVELY EXPOSED SUPPORT WITH SAID WATERSOLUBLE METALLIC COMPOUND IN THE PRESENCE OF MOISTURE, THEREBY FORMINGAN INTERNAL LATENT IMAGE CONTAINING FREE METAL SELECTED FROM THE GROUPCONSISTING OF SILVER AND MERCURY AT THE EXPOSED AREAS AND PHYSICALLYDEVELOPING SAID LATENT IMAGE BY TREATMENT WITH A DEVELOPING SOLUTIONCOMPRISING AN AQUEOUS SOLUTION OF A WATER SOLUBLE REDUCIBLE SALT OF ANOBLE METAL SELECTED FROM THE GROUP CONSISTING OF SILVER, GOLD ANDPLATINUM, SAID DEVELOPING STABILIZED SOLUTION BEING STABILIZED WITH ANIONIC SURFACE ACTIVE COMPOUND FOR A TIME AT LEAST SUFFICIENT TO CAUSESAID INTERNAL IMAGE TO GROW INTO AN EXTERNAL ELECTRICALLY CONDUCTIVEPATTERN OF SAID NOBLE-METAL.